Preparatory refactoring for compiling guc-file.c standalone

Mostly this involves moving ProcessConfigFileInternal() to guc.c
and fixing the shared API to match.

Reviewed by Andres Freund
Discussion: https://www.postgresql.org/message-id/20220810171935.7k5zgnjwqzalzmtm%40awork3.anarazel.de
Discussion: https://www.postgresql.org/message-id/CAFBsxsF8Gc2StS3haXofshHCzqNMRXiSxvQEYGwnFsTmsdwNeg@mail.gmail.com

Author: j-naylor

src/backend/utils/misc/guc-file.l

@@ -49,12 +49,6 @@ static sigjmp_buf *GUC_flex_fatal_jmp;
 
 static void FreeConfigVariable(ConfigVariable *item);
 
-static void record_config_file_error(const char *errmsg,
-									 const char *config_file,
-									 int lineno,
-									 ConfigVariable **head_p,
-									 ConfigVariable **tail_p);
-
 static int	GUC_flex_fatal(const char *msg);
 
 /* LCOV_EXCL_START */
@@ -160,358 +154,6 @@ ProcessConfigFile(GucContext context)
 	MemoryContextDelete(config_cxt);
 }
 
-/*
- * This function handles both actual config file (re)loads and execution of
- * show_all_file_settings() (i.e., the pg_file_settings view).  In the latter
- * case we don't apply any of the settings, but we make all the usual validity
- * checks, and we return the ConfigVariable list so that it can be printed out
- * by show_all_file_settings().
- */
-static ConfigVariable *
-ProcessConfigFileInternal(GucContext context, bool applySettings, int elevel)
-{
-	bool		error = false;
-	bool		applying = false;
-	const char *ConfFileWithError;
-	ConfigVariable *item,
-			   *head,
-			   *tail;
-	int			i;
-
-	/* Parse the main config file into a list of option names and values */
-	ConfFileWithError = ConfigFileName;
-	head = tail = NULL;
-
-	if (!ParseConfigFile(ConfigFileName, true,
-						 NULL, 0, 0, elevel,
-						 &head, &tail))
-	{
-		/* Syntax error(s) detected in the file, so bail out */
-		error = true;
-		goto bail_out;
-	}
-
-	/*
-	 * Parse the PG_AUTOCONF_FILENAME file, if present, after the main file to
-	 * replace any parameters set by ALTER SYSTEM command.  Because this file
-	 * is in the data directory, we can't read it until the DataDir has been
-	 * set.
-	 */
-	if (DataDir)
-	{
-		if (!ParseConfigFile(PG_AUTOCONF_FILENAME, false,
-							 NULL, 0, 0, elevel,
-							 &head, &tail))
-		{
-			/* Syntax error(s) detected in the file, so bail out */
-			error = true;
-			ConfFileWithError = PG_AUTOCONF_FILENAME;
-			goto bail_out;
-		}
-	}
-	else
-	{
-		/*
-		 * If DataDir is not set, the PG_AUTOCONF_FILENAME file cannot be
-		 * read.  In this case, we don't want to accept any settings but
-		 * data_directory from postgresql.conf, because they might be
-		 * overwritten with settings in the PG_AUTOCONF_FILENAME file which
-		 * will be read later. OTOH, since data_directory isn't allowed in the
-		 * PG_AUTOCONF_FILENAME file, it will never be overwritten later.
-		 */
-		ConfigVariable *newlist = NULL;
-
-		/*
-		 * Prune all items except the last "data_directory" from the list.
-		 */
-		for (item = head; item; item = item->next)
-		{
-			if (!item->ignore &&
-				strcmp(item->name, "data_directory") == 0)
-				newlist = item;
-		}
-
-		if (newlist)
-			newlist->next = NULL;
-		head = tail = newlist;
-
-		/*
-		 * Quick exit if data_directory is not present in file.
-		 *
-		 * We need not do any further processing, in particular we don't set
-		 * PgReloadTime; that will be set soon by subsequent full loading of
-		 * the config file.
-		 */
-		if (head == NULL)
-			goto bail_out;
-	}
-
-	/*
-	 * Mark all extant GUC variables as not present in the config file. We
-	 * need this so that we can tell below which ones have been removed from
-	 * the file since we last processed it.
-	 */
-	for (i = 0; i < num_guc_variables; i++)
-	{
-		struct config_generic *gconf = guc_variables[i];
-
-		gconf->status &= ~GUC_IS_IN_FILE;
-	}
-
-	/*
-	 * Check if all the supplied option names are valid, as an additional
-	 * quasi-syntactic check on the validity of the config file.  It is
-	 * important that the postmaster and all backends agree on the results of
-	 * this phase, else we will have strange inconsistencies about which
-	 * processes accept a config file update and which don't.  Hence, unknown
-	 * custom variable names have to be accepted without complaint.  For the
-	 * same reason, we don't attempt to validate the options' values here.
-	 *
-	 * In addition, the GUC_IS_IN_FILE flag is set on each existing GUC
-	 * variable mentioned in the file; and we detect duplicate entries in the
-	 * file and mark the earlier occurrences as ignorable.
-	 */
-	for (item = head; item; item = item->next)
-	{
-		struct config_generic *record;
-
-		/* Ignore anything already marked as ignorable */
-		if (item->ignore)
-			continue;
-
-		/*
-		 * Try to find the variable; but do not create a custom placeholder if
-		 * it's not there already.
-		 */
-		record = find_option(item->name, false, true, elevel);
-
-		if (record)
-		{
-			/* If it's already marked, then this is a duplicate entry */
-			if (record->status & GUC_IS_IN_FILE)
-			{
-				/*
-				 * Mark the earlier occurrence(s) as dead/ignorable.  We could
-				 * avoid the O(N^2) behavior here with some additional state,
-				 * but it seems unlikely to be worth the trouble.
-				 */
-				ConfigVariable *pitem;
-
-				for (pitem = head; pitem != item; pitem = pitem->next)
-				{
-					if (!pitem->ignore &&
-						strcmp(pitem->name, item->name) == 0)
-						pitem->ignore = true;
-				}
-			}
-			/* Now mark it as present in file */
-			record->status |= GUC_IS_IN_FILE;
-		}
-		else if (!valid_custom_variable_name(item->name))
-		{
-			/* Invalid non-custom variable, so complain */
-			ereport(elevel,
-					(errcode(ERRCODE_UNDEFINED_OBJECT),
-					 errmsg("unrecognized configuration parameter \"%s\" in file \"%s\" line %d",
-							item->name,
-							item->filename, item->sourceline)));
-			item->errmsg = pstrdup("unrecognized configuration parameter");
-			error = true;
-			ConfFileWithError = item->filename;
-		}
-	}
-
-	/*
-	 * If we've detected any errors so far, we don't want to risk applying any
-	 * changes.
-	 */
-	if (error)
-		goto bail_out;
-
-	/* Otherwise, set flag that we're beginning to apply changes */
-	applying = true;
-
-	/*
-	 * Check for variables having been removed from the config file, and
-	 * revert their reset values (and perhaps also effective values) to the
-	 * boot-time defaults.  If such a variable can't be changed after startup,
-	 * report that and continue.
-	 */
-	for (i = 0; i < num_guc_variables; i++)
-	{
-		struct config_generic *gconf = guc_variables[i];
-		GucStack   *stack;
-
-		if (gconf->reset_source != PGC_S_FILE ||
-			(gconf->status & GUC_IS_IN_FILE))
-			continue;
-		if (gconf->context < PGC_SIGHUP)
-		{
-			/* The removal can't be effective without a restart */
-			gconf->status |= GUC_PENDING_RESTART;
-			ereport(elevel,
-					(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
-					 errmsg("parameter \"%s\" cannot be changed without restarting the server",
-							gconf->name)));
-			record_config_file_error(psprintf("parameter \"%s\" cannot be changed without restarting the server",
-											  gconf->name),
-									 NULL, 0,
-									 &head, &tail);
-			error = true;
-			continue;
-		}
-
-		/* No more to do if we're just doing show_all_file_settings() */
-		if (!applySettings)
-			continue;
-
-		/*
-		 * Reset any "file" sources to "default", else set_config_option will
-		 * not override those settings.
-		 */
-		if (gconf->reset_source == PGC_S_FILE)
-			gconf->reset_source = PGC_S_DEFAULT;
-		if (gconf->source == PGC_S_FILE)
-			gconf->source = PGC_S_DEFAULT;
-		for (stack = gconf->stack; stack; stack = stack->prev)
-		{
-			if (stack->source == PGC_S_FILE)
-				stack->source = PGC_S_DEFAULT;
-		}
-
-		/* Now we can re-apply the wired-in default (i.e., the boot_val) */
-		if (set_config_option(gconf->name, NULL,
-							  context, PGC_S_DEFAULT,
-							  GUC_ACTION_SET, true, 0, false) > 0)
-		{
-			/* Log the change if appropriate */
-			if (context == PGC_SIGHUP)
-				ereport(elevel,
-						(errmsg("parameter \"%s\" removed from configuration file, reset to default",
-								gconf->name)));
-		}
-	}
-
-	/*
-	 * Restore any variables determined by environment variables or
-	 * dynamically-computed defaults.  This is a no-op except in the case
-	 * where one of these had been in the config file and is now removed.
-	 *
-	 * In particular, we *must not* do this during the postmaster's initial
-	 * loading of the file, since the timezone functions in particular should
-	 * be run only after initialization is complete.
-	 *
-	 * XXX this is an unmaintainable crock, because we have to know how to set
-	 * (or at least what to call to set) every non-PGC_INTERNAL variable that
-	 * could potentially have PGC_S_DYNAMIC_DEFAULT or PGC_S_ENV_VAR source.
-	 */
-	if (context == PGC_SIGHUP && applySettings)
-	{
-		InitializeGUCOptionsFromEnvironment();
-		pg_timezone_abbrev_initialize();
-		/* this selects SQL_ASCII in processes not connected to a database */
-		SetConfigOption("client_encoding", GetDatabaseEncodingName(),
-						PGC_BACKEND, PGC_S_DYNAMIC_DEFAULT);
-	}
-
-	/*
-	 * Now apply the values from the config file.
-	 */
-	for (item = head; item; item = item->next)
-	{
-		char	   *pre_value = NULL;
-		int			scres;
-
-		/* Ignore anything marked as ignorable */
-		if (item->ignore)
-			continue;
-
-		/* In SIGHUP cases in the postmaster, we want to report changes */
-		if (context == PGC_SIGHUP && applySettings && !IsUnderPostmaster)
-		{
-			const char *preval = GetConfigOption(item->name, true, false);
-
-			/* If option doesn't exist yet or is NULL, treat as empty string */
-			if (!preval)
-				preval = "";
-			/* must dup, else might have dangling pointer below */
-			pre_value = pstrdup(preval);
-		}
-
-		scres = set_config_option(item->name, item->value,
-								  context, PGC_S_FILE,
-								  GUC_ACTION_SET, applySettings, 0, false);
-		if (scres > 0)
-		{
-			/* variable was updated, so log the change if appropriate */
-			if (pre_value)
-			{
-				const char *post_value = GetConfigOption(item->name, true, false);
-
-				if (!post_value)
-					post_value = "";
-				if (strcmp(pre_value, post_value) != 0)
-					ereport(elevel,
-							(errmsg("parameter \"%s\" changed to \"%s\"",
-									item->name, item->value)));
-			}
-			item->applied = true;
-		}
-		else if (scres == 0)
-		{
-			error = true;
-			item->errmsg = pstrdup("setting could not be applied");
-			ConfFileWithError = item->filename;
-		}
-		else
-		{
-			/* no error, but variable's active value was not changed */
-			item->applied = true;
-		}
-
-		/*
-		 * We should update source location unless there was an error, since
-		 * even if the active value didn't change, the reset value might have.
-		 * (In the postmaster, there won't be a difference, but it does matter
-		 * in backends.)
-		 */
-		if (scres != 0 && applySettings)
-			set_config_sourcefile(item->name, item->filename,
-								  item->sourceline);
-
-		if (pre_value)
-			pfree(pre_value);
-	}
-
-	/* Remember when we last successfully loaded the config file. */
-	if (applySettings)
-		PgReloadTime = GetCurrentTimestamp();
-
-bail_out:
-	if (error && applySettings)
-	{
-		/* During postmaster startup, any error is fatal */
-		if (context == PGC_POSTMASTER)
-			ereport(ERROR,
-					(errcode(ERRCODE_CONFIG_FILE_ERROR),
-					 errmsg("configuration file \"%s\" contains errors",
-							ConfFileWithError)));
-		else if (applying)
-			ereport(elevel,
-					(errcode(ERRCODE_CONFIG_FILE_ERROR),
-					 errmsg("configuration file \"%s\" contains errors; unaffected changes were applied",
-							ConfFileWithError)));
-		else
-			ereport(elevel,
-					(errcode(ERRCODE_CONFIG_FILE_ERROR),
-					 errmsg("configuration file \"%s\" contains errors; no changes were applied",
-							ConfFileWithError)));
-	}
-
-	/* Successful or otherwise, return the collected data list */
-	return head;
-}
-
 /*
  * Given a configuration file or directory location that may be a relative
  * path, return an absolute one.  We consider the location to be relative to
@@ -660,7 +302,7 @@ cleanup:
  * Capture an error message in the ConfigVariable list returned by
  * config file parsing.
  */
-static void
+void
 record_config_file_error(const char *errmsg,
 						 const char *config_file,
 						 int lineno,

src/backend/utils/misc/guc.c

@@ -243,10 +243,6 @@ static void assign_recovery_target_lsn(const char *newval, void *extra);
 static bool check_primary_slot_name(char **newval, void **extra, GucSource source);
 static bool check_default_with_oids(bool *newval, void **extra, GucSource source);
 
-/* Private functions in guc-file.l that need to be called from guc.c */
-static ConfigVariable *ProcessConfigFileInternal(GucContext context,
-												 bool applySettings, int elevel);
-
 /*
  * Track whether there were any deferred checks for custom resource managers
  * specified in wal_consistency_checking.
@@ -5160,8 +5156,8 @@ static bool report_needed;		/* true if any GUC_REPORT reports are needed */
 static int	GUCNestLevel = 0;	/* 1 when in main transaction */
 
 
+static struct config_generic *find_option(const char *name, bool create_placeholders, bool skip_errors, int elevel);
 static int	guc_var_compare(const void *a, const void *b);
-static int	guc_name_compare(const char *namea, const char *nameb);
 static void InitializeGUCOptionsFromEnvironment(void);
 static void InitializeOneGUCOption(struct config_generic *gconf);
 static void push_old_value(struct config_generic *gconf, GucAction action);
@@ -5180,7 +5176,359 @@ static bool validate_option_array_item(const char *name, const char *value,
 static void write_auto_conf_file(int fd, const char *filename, ConfigVariable *head_p);
 static void replace_auto_config_value(ConfigVariable **head_p, ConfigVariable **tail_p,
 									  const char *name, const char *value);
+static bool valid_custom_variable_name(const char *name);
+
+/*
+ * This function handles both actual config file (re)loads and execution of
+ * show_all_file_settings() (i.e., the pg_file_settings view).  In the latter
+ * case we don't apply any of the settings, but we make all the usual validity
+ * checks, and we return the ConfigVariable list so that it can be printed out
+ * by show_all_file_settings().
+ */
+ConfigVariable *
+ProcessConfigFileInternal(GucContext context, bool applySettings, int elevel)
+{
+	bool		error = false;
+	bool		applying = false;
+	const char *ConfFileWithError;
+	ConfigVariable *item,
+			   *head,
+			   *tail;
+	int			i;
+
+	/* Parse the main config file into a list of option names and values */
+	ConfFileWithError = ConfigFileName;
+	head = tail = NULL;
+
+	if (!ParseConfigFile(ConfigFileName, true,
+						 NULL, 0, 0, elevel,
+						 &head, &tail))
+	{
+		/* Syntax error(s) detected in the file, so bail out */
+		error = true;
+		goto bail_out;
+	}
+
+	/*
+	 * Parse the PG_AUTOCONF_FILENAME file, if present, after the main file to
+	 * replace any parameters set by ALTER SYSTEM command.  Because this file
+	 * is in the data directory, we can't read it until the DataDir has been
+	 * set.
+	 */
+	if (DataDir)
+	{
+		if (!ParseConfigFile(PG_AUTOCONF_FILENAME, false,
+							 NULL, 0, 0, elevel,
+							 &head, &tail))
+		{
+			/* Syntax error(s) detected in the file, so bail out */
+			error = true;
+			ConfFileWithError = PG_AUTOCONF_FILENAME;
+			goto bail_out;
+		}
+	}
+	else
+	{
+		/*
+		 * If DataDir is not set, the PG_AUTOCONF_FILENAME file cannot be
+		 * read.  In this case, we don't want to accept any settings but
+		 * data_directory from postgresql.conf, because they might be
+		 * overwritten with settings in the PG_AUTOCONF_FILENAME file which
+		 * will be read later. OTOH, since data_directory isn't allowed in the
+		 * PG_AUTOCONF_FILENAME file, it will never be overwritten later.
+		 */
+		ConfigVariable *newlist = NULL;
+
+		/*
+		 * Prune all items except the last "data_directory" from the list.
+		 */
+		for (item = head; item; item = item->next)
+		{
+			if (!item->ignore &&
+				strcmp(item->name, "data_directory") == 0)
+				newlist = item;
+		}
 
+		if (newlist)
+			newlist->next = NULL;
+		head = tail = newlist;
+
+		/*
+		 * Quick exit if data_directory is not present in file.
+		 *
+		 * We need not do any further processing, in particular we don't set
+		 * PgReloadTime; that will be set soon by subsequent full loading of
+		 * the config file.
+		 */
+		if (head == NULL)
+			goto bail_out;
+	}
+
+	/*
+	 * Mark all extant GUC variables as not present in the config file. We
+	 * need this so that we can tell below which ones have been removed from
+	 * the file since we last processed it.
+	 */
+	for (i = 0; i < num_guc_variables; i++)
+	{
+		struct config_generic *gconf = guc_variables[i];
+
+		gconf->status &= ~GUC_IS_IN_FILE;
+	}
+
+	/*
+	 * Check if all the supplied option names are valid, as an additional
+	 * quasi-syntactic check on the validity of the config file.  It is
+	 * important that the postmaster and all backends agree on the results of
+	 * this phase, else we will have strange inconsistencies about which
+	 * processes accept a config file update and which don't.  Hence, unknown
+	 * custom variable names have to be accepted without complaint.  For the
+	 * same reason, we don't attempt to validate the options' values here.
+	 *
+	 * In addition, the GUC_IS_IN_FILE flag is set on each existing GUC
+	 * variable mentioned in the file; and we detect duplicate entries in the
+	 * file and mark the earlier occurrences as ignorable.
+	 */
+	for (item = head; item; item = item->next)
+	{
+		struct config_generic *record;
+
+		/* Ignore anything already marked as ignorable */
+		if (item->ignore)
+			continue;
+
+		/*
+		 * Try to find the variable; but do not create a custom placeholder if
+		 * it's not there already.
+		 */
+		record = find_option(item->name, false, true, elevel);
+
+		if (record)
+		{
+			/* If it's already marked, then this is a duplicate entry */
+			if (record->status & GUC_IS_IN_FILE)
+			{
+				/*
+				 * Mark the earlier occurrence(s) as dead/ignorable.  We could
+				 * avoid the O(N^2) behavior here with some additional state,
+				 * but it seems unlikely to be worth the trouble.
+				 */
+				ConfigVariable *pitem;
+
+				for (pitem = head; pitem != item; pitem = pitem->next)
+				{
+					if (!pitem->ignore &&
+						strcmp(pitem->name, item->name) == 0)
+						pitem->ignore = true;
+				}
+			}
+			/* Now mark it as present in file */
+			record->status |= GUC_IS_IN_FILE;
+		}
+		else if (!valid_custom_variable_name(item->name))
+		{
+			/* Invalid non-custom variable, so complain */
+			ereport(elevel,
+					(errcode(ERRCODE_UNDEFINED_OBJECT),
+					 errmsg("unrecognized configuration parameter \"%s\" in file \"%s\" line %d",
+							item->name,
+							item->filename, item->sourceline)));
+			item->errmsg = pstrdup("unrecognized configuration parameter");
+			error = true;
+			ConfFileWithError = item->filename;
+		}
+	}
+
+	/*
+	 * If we've detected any errors so far, we don't want to risk applying any
+	 * changes.
+	 */
+	if (error)
+		goto bail_out;
+
+	/* Otherwise, set flag that we're beginning to apply changes */
+	applying = true;
+
+	/*
+	 * Check for variables having been removed from the config file, and
+	 * revert their reset values (and perhaps also effective values) to the
+	 * boot-time defaults.  If such a variable can't be changed after startup,
+	 * report that and continue.
+	 */
+	for (i = 0; i < num_guc_variables; i++)
+	{
+		struct config_generic *gconf = guc_variables[i];
+		GucStack   *stack;
+
+		if (gconf->reset_source != PGC_S_FILE ||
+			(gconf->status & GUC_IS_IN_FILE))
+			continue;
+		if (gconf->context < PGC_SIGHUP)
+		{
+			/* The removal can't be effective without a restart */
+			gconf->status |= GUC_PENDING_RESTART;
+			ereport(elevel,
+					(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
+					 errmsg("parameter \"%s\" cannot be changed without restarting the server",
+							gconf->name)));
+			record_config_file_error(psprintf("parameter \"%s\" cannot be changed without restarting the server",
+											  gconf->name),
+									 NULL, 0,
+									 &head, &tail);
+			error = true;
+			continue;
+		}
+
+		/* No more to do if we're just doing show_all_file_settings() */
+		if (!applySettings)
+			continue;
+
+		/*
+		 * Reset any "file" sources to "default", else set_config_option will
+		 * not override those settings.
+		 */
+		if (gconf->reset_source == PGC_S_FILE)
+			gconf->reset_source = PGC_S_DEFAULT;
+		if (gconf->source == PGC_S_FILE)
+			gconf->source = PGC_S_DEFAULT;
+		for (stack = gconf->stack; stack; stack = stack->prev)
+		{
+			if (stack->source == PGC_S_FILE)
+				stack->source = PGC_S_DEFAULT;
+		}
+
+		/* Now we can re-apply the wired-in default (i.e., the boot_val) */
+		if (set_config_option(gconf->name, NULL,
+							  context, PGC_S_DEFAULT,
+							  GUC_ACTION_SET, true, 0, false) > 0)
+		{
+			/* Log the change if appropriate */
+			if (context == PGC_SIGHUP)
+				ereport(elevel,
+						(errmsg("parameter \"%s\" removed from configuration file, reset to default",
+								gconf->name)));
+		}
+	}
+
+	/*
+	 * Restore any variables determined by environment variables or
+	 * dynamically-computed defaults.  This is a no-op except in the case
+	 * where one of these had been in the config file and is now removed.
+	 *
+	 * In particular, we *must not* do this during the postmaster's initial
+	 * loading of the file, since the timezone functions in particular should
+	 * be run only after initialization is complete.
+	 *
+	 * XXX this is an unmaintainable crock, because we have to know how to set
+	 * (or at least what to call to set) every non-PGC_INTERNAL variable that
+	 * could potentially have PGC_S_DYNAMIC_DEFAULT or PGC_S_ENV_VAR source.
+	 */
+	if (context == PGC_SIGHUP && applySettings)
+	{
+		InitializeGUCOptionsFromEnvironment();
+		pg_timezone_abbrev_initialize();
+		/* this selects SQL_ASCII in processes not connected to a database */
+		SetConfigOption("client_encoding", GetDatabaseEncodingName(),
+						PGC_BACKEND, PGC_S_DYNAMIC_DEFAULT);
+	}
+
+	/*
+	 * Now apply the values from the config file.
+	 */
+	for (item = head; item; item = item->next)
+	{
+		char	   *pre_value = NULL;
+		int			scres;
+
+		/* Ignore anything marked as ignorable */
+		if (item->ignore)
+			continue;
+
+		/* In SIGHUP cases in the postmaster, we want to report changes */
+		if (context == PGC_SIGHUP && applySettings && !IsUnderPostmaster)
+		{
+			const char *preval = GetConfigOption(item->name, true, false);
+
+			/* If option doesn't exist yet or is NULL, treat as empty string */
+			if (!preval)
+				preval = "";
+			/* must dup, else might have dangling pointer below */
+			pre_value = pstrdup(preval);
+		}
+
+		scres = set_config_option(item->name, item->value,
+								  context, PGC_S_FILE,
+								  GUC_ACTION_SET, applySettings, 0, false);
+		if (scres > 0)
+		{
+			/* variable was updated, so log the change if appropriate */
+			if (pre_value)
+			{
+				const char *post_value = GetConfigOption(item->name, true, false);
+
+				if (!post_value)
+					post_value = "";
+				if (strcmp(pre_value, post_value) != 0)
+					ereport(elevel,
+							(errmsg("parameter \"%s\" changed to \"%s\"",
+									item->name, item->value)));
+			}
+			item->applied = true;
+		}
+		else if (scres == 0)
+		{
+			error = true;
+			item->errmsg = pstrdup("setting could not be applied");
+			ConfFileWithError = item->filename;
+		}
+		else
+		{
+			/* no error, but variable's active value was not changed */
+			item->applied = true;
+		}
+
+		/*
+		 * We should update source location unless there was an error, since
+		 * even if the active value didn't change, the reset value might have.
+		 * (In the postmaster, there won't be a difference, but it does matter
+		 * in backends.)
+		 */
+		if (scres != 0 && applySettings)
+			set_config_sourcefile(item->name, item->filename,
+								  item->sourceline);
+
+		if (pre_value)
+			pfree(pre_value);
+	}
+
+	/* Remember when we last successfully loaded the config file. */
+	if (applySettings)
+		PgReloadTime = GetCurrentTimestamp();
+
+bail_out:
+	if (error && applySettings)
+	{
+		/* During postmaster startup, any error is fatal */
+		if (context == PGC_POSTMASTER)
+			ereport(ERROR,
+					(errcode(ERRCODE_CONFIG_FILE_ERROR),
+					 errmsg("configuration file \"%s\" contains errors",
+							ConfFileWithError)));
+		else if (applying)
+			ereport(elevel,
+					(errcode(ERRCODE_CONFIG_FILE_ERROR),
+					 errmsg("configuration file \"%s\" contains errors; unaffected changes were applied",
+							ConfFileWithError)));
+		else
+			ereport(elevel,
+					(errcode(ERRCODE_CONFIG_FILE_ERROR),
+					 errmsg("configuration file \"%s\" contains errors; no changes were applied",
+							ConfFileWithError)));
+	}
+
+	/* Successful or otherwise, return the collected data list */
+	return head;
+}
 
 /*
  * Some infrastructure for checking malloc/strdup/realloc calls
@@ -5737,7 +6085,7 @@ guc_var_compare(const void *a, const void *b)
 /*
  * the bare comparison function for GUC names
  */
-static int
+int
 guc_name_compare(const char *namea, const char *nameb)
 {
 	/*

src/include/utils/guc.h

@@ -442,6 +442,15 @@ extern void GUC_check_errcode(int sqlerrcode);
 	pre_format_elog_string(errno, TEXTDOMAIN), \
 	GUC_check_errhint_string = format_elog_string
 
+/* functions shared between guc.c and guc-file.l */
+extern int	guc_name_compare(const char *namea, const char *nameb);
+extern ConfigVariable *ProcessConfigFileInternal(GucContext context,
+												 bool applySettings, int elevel);
+extern void record_config_file_error(const char *errmsg,
+									 const char *config_file,
+									 int lineno,
+									 ConfigVariable **head_p,
+									 ConfigVariable **tail_p);
 
 /*
  * The following functions are not in guc.c, but are declared here to avoid